Parenchyma is distributed in almost all parts of the plant body. It is the most simple and primitive tissue from which other tissues are evolved. The main function of parenchyma is storage of food. In xerophytes, it helps in storage of water. Parenchyma with abundant chloroplasts is called chlorenchyma & the function of it is photosynthesis. Fibre like elongated cells of parenchyma provides rigidity & strength. It also provides protection to epidermis of stem & leaf. It also takes part in excretion in many ways like gum, rubber, etc.

Photosynthesis:
- Parenchyma cells are responsible for performing photosynthesis in plants.
- These cells contain chloroplasts, which are responsible for capturing sunlight and converting it into energy through the process of photosynthesis.
- The chloroplasts contain chlorophyll, which gives plants their green color and is essential for photosynthesis.

Storage:
- Parenchyma cells also play a crucial role in storing various substances in plants.
- These cells have large vacuoles that can store water, nutrients, and other substances.
- The storage function of parenchyma cells helps in maintaining the overall health and well-being of the plant.
- Examples of storage tissues in plants include the pith in stems and the cortex in roots.

Excretion:
- Parenchyma cells are involved in excretion by helping in the elimination of waste products from the plant.
- These cells are responsible for the excretion of metabolic by-products and toxic substances.
- The waste products are transported to the vacuoles within the parenchyma cells and are eventually eliminated from the plant.

Other Functions:
- Parenchyma cells are also involved in other important functions in plants.
- They provide support to the plant by maintaining the turgidity of tissues.
- These cells also participate in the repair and regeneration of plant tissues.
- Parenchyma cells can differentiate into other types of cells when needed, such as during wound healing or the formation of new roots.

Sclerenchyma, Collenchyma, and Aerenchyma:
- Sclerenchyma cells are mainly responsible for providing structural support to the plant.
- Collenchyma cells provide flexible support to plant organs, allowing them to bend without breaking.
- Aerenchyma is a specialized type of parenchyma tissue that contains air spaces, allowing for gas exchange in aquatic plants.

Therefore, the correct answer is option B, Parenchyma, as it performs various functions like photosynthesis, storage, and excretion in plants.